The present invention relates to a fuel injection system for externally ignited internal combustion engines.
The system comprises a distributor unit and metering valves wherein metering is effected with a constant pressure difference. The metering valves are displaceable in common so as to vary their flow passage section and regulate the quantity of fuel flowing to the injection nozzles. In the fuel flow downstream of each of the metering valves there is connected a valve, the flow passage section of which may be varied by a flexible member separating two chambers, in the first chamber of which the pressure urges the flexible member in an opening direction. At least one of the valves, downstream of the metering valves, is in the form of a constant pressure valve, while at least one valve is in the form of a differential pressure control valve, the first chamber of which communicates with the second chamber of each constant pressure valve.
The purpose of the above-mentioned type of injection system is to obtain a corresponding change in the flow passage section of the metering valves with the regulated fuel quantity corresponding to the operating conditions of the engine acting on the metering valve and by means of as constant a pressure drop as possible through this flow passage section resulting in a uniform, exact metering of fuel as a function of the magnitude of the flow passage section, and with such metering being independent of the pressures downstream or upstream of the metering point.
In the known injection systems of this type the fuel for the individual cylinders of the engine is metered collectively by a leading edges of a servo valve spool at different control slots. While metering is carried out, a constant pressure difference is maintained which is electromagnetically varied as a function of the engine characteristics by means of a differential pressure control valve. However, this necessitates a relatively high construction cost.